This invention relates to the preparation of polyether polymers and intermediates therefor. More particularly, it relates to the preparation of bis(halophthalimides), their isolation as a slurry and their use in slurry form for the preparation of polyetherimides.
Various types of aromatic polyethers, particularly polyetherimides but also including polyethersulfones, polyetherketones, and polyetheretherketones, have become important as engineering resins by reason of their excellent properties. These polymers are typically prepared by the reaction of salts of dihydroxyaromatic compounds, such as bisphenol A disodium salt, with dihaloaromatic molecules. For example, polyetherimides are conveniently prepared by the reaction of salts of dihydroxyaromatic compounds with bis(halophthalimides) as illustrated by 1,3-bis[N-(4-chlorophthalimido)]benzene (hereinafter sometimes "ClPAMI"), which has the structure ##STR1##
For polysulfones and polyetherketones, bis(4-fluorophenyl) sulfone, bis(4-chlorophenyl) sulfone and the analogous ketones are typically employed.
According to U.S. Pat. Nos. 5,229,482 and 5,830,974, the preparation of aromatic polyethers may be conducted in solution in relatively non-polar solvents, using a phase transfer catalyst which is substantially stable under the temperature conditions employed. Solvents disclosed in U.S. Pat. No. 5,229,482 include o-dichlorobenzene, dichlorotoluene, 1,2,4-trichlorobenzene and diphenyl sulfone. In U.S. Pat. No. 5,830,974, monoalkoxybenzenes such as anisole, diphenylether, or phenetole are employed. Solvents of the same types may be used for the preparation of bis(halophthalimide) intermediates for polyetherimides.
Each of these patents requires introduction into the reaction mixture of the bis(halophthalimide) as a substantially pure, isolated compound. This is often difficult, since solid bis(halophthalimides) are typically of very low density and fluffy, making weighing and handling burdensome. It would be desirable, for both technical and cost reasons, to handle such reactants as slurries in an organic solvent instead of in dry solid form.
In order to isolate bis(halophthalimides) in slurry form, however, it is often preferred to prepare them by a method which employs the reactants, namely diamino compound and halophthalic anhydride, in equimolar proportions so as to avoid competing reactions. According to such prior art as U.S. Pat. No. 3,787,364, the employment of substantially equimolar proportions of reactants can result in the necessity for extremely long reaction times, typically up to 3 days. This is true even when such active solvents as glacial acetic acid are employed. When non-polar solvents are employed, it has typically been necessary to employ one reactant, most often the chlorophthalic anhydride, in excess, whereupon said reactant is still present after completion of the reaction and can cause competing reactions to take place upon synthesis of the polyetherimide.